Healing of transplanted composite bone grafts-implants: a pilot animal study

This experimental pilot study was undertaken to evaluate healing of titanium implants transplanted with the surrounding bone into recipient osseous sites in the rabbit mandible. One short implant was inserted in the horizontal portion of the mandible in each of 10 New Zealand rabbits. Subsequently, and during the same session, the implant with 1.5-2.0 mm of bone circumferentially was removed using a trephine bur and immediately transplanted in a through-and-through hole prepared in the contralateral aspect of the mandible. Three months following the transplantation, the animals were sacrificed and the mandibles processed for histological evaluation. The healing pattern was assessed in relation to (1) bone bridging at the interface between the bone core and the surrounding recipient osseous tissue, (2) differences in bone density between the transplanted bone cylinder and the bone at the margins of the recipient site, and (3) bone-to-implant contact (BIC) at the interface. The transplanted graft-implant cores were integrated within the recipient sites in five out of the 10 specimens while the remaining five bone-implant cores showed fibrous encapsulation. Various patterns of resorption were observed within the peri-implant transplanted hard tissues. Percentage BIC ranged between 1% and 72% in the fibrous-encapsulated specimens and between 20% and 62% in the integrated transplants. Within the limits of this pilot study, the results suggest that immediate transplantation of endosseous implants with their surrounding bone into congruous recipient osseous sites cannot predictably yield graft-implant incorporation and osseointegration of the implants. This alternative surgical modality of immediately transplanting a composite bone graft-implant from highly cortical intraoral or extraoral sites to enhance bone quality and/or volume in implant recipient sites such as the maxillary sinus and tuberosity areas needs to be further investigated.